User:Michaela Harper/Notebook/Biological Chemistry Lab/2011/08/31

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Objective

To use BSA (bovine serum albumin) to synthesize gold nanoparticles. BSA reduces Au3+ to Au 0 for the synthesis to occur.

Description

• Add 0.0015 mM BSA and 0.25 mM of HAuCl4 to 10 mL of 50mM acetate buffer (pH 5.46) at room temperature. The ratio of Au to BSA is 167 for optimum results.
• Note: distilled water used to rinse gold and BSA into mixture from weigh boats.
• Four-place balance used to determine weights. Actual weights determined to be 0.0011g BSA and 0.0004g gold.
• Heat mixture at 80°C for four hours (actual temperature varies closer to 70°C).
• Using a UV-Vis Spectrophotometer, obtain spectra every 30 minutes, starting at t=0 minutes
• Calculations:
Au
0.25mM Au = 0.00025 mol / L = 2.5 x 10-7 mol / mL
2.5 x 10-7 mol / mL = x / 10 mL
x = 2.5 x 10-6 mol / mL x 196.967 g/mol = 4.92 x 10-4g
BSA
0.0015mM BSA = 0.0000015 mol / L = 1.5 x 10-9 mol / mL
1.5 x 10-9 mol / mL = x / 10 mL
x = 1.5 x 10-9 mol / mL x 66776 g/mol = 1.00 x 10-3g
• The solution is covered in aluminum foil and stored at room temperature overnight.

Data

This graph shows the absorbance for each spectrum taken every 30 minutes. First, a blank spectrum of the buffer solution was taken and subracted from each of the following spectra to create a corrected absorbance. Series 1 represents the spectra taken at t=0, series 2 represents the spectra taken at t=30 minutes, etc up to series 6 representing t=150 minutes.

I would also like to see this graph zoomed in to the features at 550. The thing I would like to know is: Are the changes at 550nm due to a new feature in the spectrum or just an increase in the baseline<b> Matt Hartings 08:53, 6 September 2011 (EDT)

This graph shows the corrected absorbance at 550nm over time. This represents the concentration of gold nanoparticles that were formed. However, from the zoomed in graph, it is apparent that the changes are due to an increase in the baseline.

This graph shows the zoomed in features at 550nm. The changes at 550nm are due to an increase in the baseline, not a new feature.

Notes

The color of the mixture turned a very slight yellow over time, then returned to a clear color. The UV-Vis spectra were taken from 200-800nm using a 1mL quartz cuvette.